1. Field of the Invention
The present invention relates to a printer of ink circulation type, and particularly to an acquirement of temperatures of ink and a printing control based thereon.
2. Description of Related Arts
There has been spread use of inkjet printers including print heads for propelling ink droplets to make a print on a print sheet. In inkjet printers, print heads have had their ink propelling mechanisms configured with arrays of piezoelectric devices or such for propelling ink droplets in accordance with applied drive voltages. For use in inkjet printers, there have been various kinds of ink available with a typical property tending to have increased viscosities under low-temperature environments, constituting a difficulty to secure adequate droplet amounts. To this point, there has been a patent literature 1 (Japanese Patent Application Laid-Open Publication No. 2008-23806) describing a warm-up of ink in a low temperature state, with a pause of print until an arrival at an adequate ink temperature. Further, there has been practical use of inkjet printers configured with an ink circulation route therein to circulate ink for a further enhanced printing reliability.
FIG. 1 shows a configuration of combination of an inkjet head 130 and an ink circulation system 150 of a conventional ink circulation type inkjet printer. As shown in the figure, the inkjet head 130 includes ink chambers 131, ink propelling mechanisms 132, and a temperature sensor 133. The temperature sensor 133 is adapted to measure a representative ink temperature of the ink chambers 131 directly or indirectly.
The ink circulation system has a looped ink circulation mute, and includes a replaceable ink cartridge 210, a downstream tank 220, a pump 260, a cooler 250, a heater 240, and an upstream tank 230. The upstream tank 230 has a temperature sensor 231 disposed therein to measure an ink temperature. It is noted that the present figure is illustrated for only one color ink. When the inkjet printer is provided with a number of different color inks, it has an ink cartridge 210, an inkjet head 130, a downstream tank 220, an upstream tank 230, a temperature sensor 231, and the like provided for each color.
The ink cartridge 210 supplies ink, which is temporarily stored in the downstream tank 220 installed downstream of the inkjet head 130. Then, ink is delivered by the pump 260 from the downstream tank 220 to the upstream tank 230, where it is supplied to the ink chambers 131 in the inkjet head 130, where it is used for a printing. Unused ink in the inkjet head 130 is returned again to the downstream tank 220.
The heater 240 is disposed in a vicinity of the upstream tank 230, and the cooler 250 is disposed between the downstream tank 220 and the upstream tank 230. The heater 240 is adapted to warm up ink when the ink temperature is low, which is measured by the temperature sensor 231 disposed in the upstream tank 230. The cooler 250 is configured with a heat sink and an air fan, for instance, and adapted to cool ink when the ink temperature is high.